Hey, I was thinking about this today. If you used a strip of polarized film between the light and the TIR block, and then between the TIR block and your eyes put another sheet of polarizing film that's properly oriented, you should be able to filter out 90% or so or the eye-light from ever reaching your eyes, and thus only leave the return light.
Downside is that the first layer of polarizing film and the TIR block are going to knock down the amount of light that makes it out the eyes, so that means it's going to need WAY more source light.
Still, I love the idea, and I think it can go places.
Just spotted the unread comment. :S
You've already put a lot more thought in than me. I'll probably just fiddle around with some mirror film and thin plastic lenses when the helmet is finally finished, and go the Wile E Coyote route and ditch the whole thing.
If I do get it working I'll post it.
